MOG and erythema multiforme: MOG is a type of glycoprotein on oligodendrocyte which is only found in central nervous system.[11] And impairment of the blood brain barrier (BBB) may play an important role in pathogenesis of MOG-EM.[12–14] The tumor itself might represent the immune response and immune monitoring abnormalities in human beings.[6] In our case report, the impairment of BBB and oligodendrocyte might consist of four factors, including the impairment of tumor, tumor resection, postoperative radiation treatment and chemotherapy.